The invention relates to a method for producing an electrically conductive material, an electrically conductive material, and an emitter containing an electrically conductive material.
The electrically conductive materials at issue are conceivable for use as electrically heatable elements for use in incandescent lamps or infrared emitters. Accordingly, the electrically conductive materials are suitable, in particular, for the targeted emission of beams in the visible, and in particular in the non-visible, range of wavelengths.
Electrically conductive materials of this type are often based on carbon or consist mainly of carbon. However, electrically conductive materials of the type at issue, used as a starting material, can comprise various materials alternative to or in addition to carbon that provide an electrical conductivity.
In ready-to-use, pre-assembled form, the electrically conductive materials at issue can also be referred to as incandescent filament, glow wire, glow coil, heating rod, and, in particular, as filament. Insofar as reference is made to filaments hereinafter, this shall always also comprise the electrically conductive material from which the filament is made.
The manufacture of electrically conductive materials, in particular of carbon-based materials, for use as an electrically heated element for use in incandescent lamps or infrared emitters has been known for a long time. The electrically conductive materials undergo a large number of manufacturing steps aimed at preparing the materials for long-lasting use at temperatures above 800° C.
In this context, it is generally difficult to manufacture all materials and/or filaments of a production lot to be within a defined tolerance range in terms of the electrical and mechanical properties on account of variations in the properties of the starting material, and to thus ensure that the radiation source has constant, consistent properties. In this context, the electrical properties generally are to be adjusted appropriately, such that the desired power (in the case of infrared radiation) or color temperature (in the case of incandescent lamps) at a given nominal voltage and given radiation source dimensions is attained. Moreover, the electrically conductive material should comprise sufficient mechanical strength and dimensional stability. Lastly, the effort and costs involved in the manufacture of the electrically conductive material should be at a reasonable level.
Depending on the desired purpose of application of the electrically conductive materials at issue herein, the requirements mentioned above generally will vary, and various technical solutions will be selected by a person skilled in the art in order to meet the requirements. An overview of the manufacture of electrically conductive materials is provided in John W. Howell, Henry Schroeder: History of the Incandescent Lamp, The Maqua Company, Schenectady, N.Y. (1927).
The electrically conductive materials can be manufactured, for example, by enveloping fibers, which are electrically conductive, with an appropriate enveloping material. The enveloping material can then provide a suitable matrix for the electrically conductive fibers, in particular after a heat treatment is carried out.